The chemical composition of muscovite is dependent on the mineral assemblage, with Si = 6.1–6.2 per formula unit in two high alumina assemblages, versus Si = 6.6 in a low alumina assemblage. Microprobe analyses indicate that muscovite, paragonite and pyrophyllite are sometimes intergrown on a micrometre scale. Chlorite composition estimated from X-ray data shows good correspondence with microprobe data for two Al-poor samples but is less satisfactory for an Al-rich sample.

Observed mineral assemblages in AKNa are indicative of the pyrophyllite-paragonite-albite fades. For the first time, chemical data for coexisting pyrophyllite, chlorite (M = MgO/(MgO+ FeO) = 0.377) and chloritoid (M = 0.110) are given. This assemblage is indicative of the low or medium pressure range of the lower greenschist facies.

Pressure conditions during metamorphism are not well constrained but a minimum pressure of 2 kbar, corresponding to 5–6 km of overburden, can be estimated from the NaM4 content of actinolite. Temperatures derived from the calcite-dolomite geothermometer range between 300 and 350°C and are consistent with the presence of the assemblage pyrophyllite + calcite + quartz.